1. Field of Invention
This invention relates to a system for oral delivery of gases pressurized above ambient, and in particular, to a system, including a novel mouthpiece, for the oral delivery of air or gases in continuous positive airway pressure (CPAP) treatments of sleeping disorders such as sleep apnoea.
2. Description of the Prior Art
Sleep apnoea treatments have been significantly advanced with the introduction of continuous positive airway pressure (CPAP) treatments. These treatments, as introduced, involve the supply of gases from a gases supply or blower to a patient or user through a conduit and nasal mask to provide an elevated internal pressure in the user's airways to assist the muscles to keep the airways open. This air stream is provided to the user through a nasal mask applied over the nose and held in place by a harness. This configuration has been almost universally adopted based on the well-known observation that humans show a decided preference for nasal breathing during sleep. For this reason, little development has been undertaken into other possible methods of providing the pressurized air stream to a user.
Oral delivery is suggested in EP818213, which shows an apparatus for oral delivery of air in a CPAP treatment. The apparatus includes a mouthpiece adapted to fit inside the mouth between the roof of the mouth, the hard palate, and the tongue, and having a periphery that can be gripped between the teeth. It is thought by the applicants that this is significantly more intrusive than is necessary and is liable to movement and consequent discomfort (although not outright removal) under the relaxation of sleep. It has the additional disadvantage that with the user fully relaxed, such as in the case of sleep, distension in the user's jaw and subsequent opening of the mouth can reduce the sealing effectiveness of the mouthpiece and reduce the efficacy of the CPAP treatment.
The mouthpiece in EP818213 is gripped between the user's teeth; thus a further disadvantage results in that the mouthpiece requires custom orthodontic fitting to ensure that the mouthpiece matches the user's mouth and teeth layout. Custom orthodontic fitting is time consuming and removes the capability of effective mass manufacture. Consequently, the mouthpiece in EP818213 is expensive, creating a significant barrier to the adoption of the device by the user.
A similar gases delivery mouthpiece, for use with a respirator, is shown in WO90/03199. WO90/03199 discloses an orthodontic device that is adapted to be gripped between the jaws of a user and to accommodate the user's teeth within a series of upper and lower cavities. A base member of the mouthpiece is shaped and fits against the hard palate of the user. This mouthpiece again has the disadvantage of requiring custom orthodontic fitting. Furthermore, as a result of the mouthpiece's substantial thickness and size, the mouthpiece is substantially rigid in the vestibule regions of the mouth. The mouthpiece is clamped in place by an outer shield that engages the outside of the user's lips.
A paper by E Veres entitled “Clinical trial of an oral vestibular shield for the control of snoring” (Journal of the Dental Association of South Africa, January 1993) describes the use of a shield intended to be retained in the vestibule of the mouth to seal the mouth and to promote nasal breathing which has been conventionally considered to be more beneficial than oral breathing. Humidified CPAP treatments delivered orally, however, actually derive greater benefit than those delivered nasally because secondary leakage through the nasal passages during oral delivery is significantly less than oral leakage during nasal delivery. The shield depicted in the paper is formed from flexible ethylene vinyl. The shield is custom trimmed and is custom fitted by heating to a malleable temperature and deformed by applied pressure.
Other possible mouthpiece designs are shown for example by use in self contained underwater breathing apparatus systems, for example as depicted in U.S. Pat. No. 4,862,909. This mouthpiece is a mouth guard type and is clamped between the teeth. A flange extends both in front of and behind the teeth.
Prior art mouthpieces are not well adapted for use in CPAP treatments because they are intended for conscious gripping by the user, and have been found subject to accidental removal with a user in a completely relaxed state such as sleep.
A further prior art mouthpiece that is of relevance is that shown in FIGS. 1 and 2, this mouthpiece is described in co-pending U.S. patent application Ser. No. 09/629,536. Referring to FIG. 1, the mouthpiece is illustrated including an extra-oral sealing flap 100 and intra-oral sealing flap 101. The extra-oral flap 100 in its natural bias is tapered from the breathing circuit connection 104; the wide-open end of which is shaped to conform to the facial contours around the outside of the mouth of a user. The extra-oral flap 100 is constructed of flexible material, such as silicone rubber. The outer flap 100 is seen in FIG. 2 in a bent back position. When the mouthpiece 102 is inserted into the mouth of a user, the outer flap 100 is intended to be in this bent back position to aid insertion. Prior to insertion, the outer flap is bent back by simply pressing on its outer periphery 106, until it snaps into the bent back position, in which it will stay unaided.
The mouthpiece as shown in FIGS. 1 and 2 also includes a tongue depressor 103 extending from the inner face of the intra-oral sealing flap 101. The tongue depressor 103 further includes a pair of vertically extending spacers 105 which in use may abut against the roof of the wearer's mouth and ensure that the tongue cannot completely block the air passageway. This stops the sleeping user unconsciously blocking the oral passageway and reverting to nasal breathing.
With the prior art mouthpiece of FIGS. 1 and 2, while the tongue depressor ensures that the tongue does not block the gases outlet, it prevents the user from moving their tongue to moisten the inside of their mouth, causing extreme dryness inside the user's mouth. Furthermore, the tongue depressor can prevent or restrict swallowing. Thus the mouthpiece of this invention has disadvantages that cause users discomfort.